Welding machine



March 20, 1945. H. PURAT 2,372,117

WELDING MACHINE Filed Jan. 2, 1943 6 Shegts-Sheet l INVENTOR flu goFar-4Z ATTOR Y5 March 20, 1945.

H. PURAT WELDING MACHINE Filed Jan. 2, 1945 6 Sheets-Sheet 2 INVENTORATTORN 5.

March 20, 1945. H. PURAT WELDING MACHINE 6 Sheets-Sheet 4 Filed Jan. 2,1945 ib 0000M Liz INVENTOR H1150 Furai s e ATTORN 5 March 20, 1945.

H. PU RAT WELDING MACHINE Filed Jan. 2, 1943 6 Sheets-Sheet 5 TORZIINVENTOR I 1 1 I l 1 r I II n u w wn l l "NW N WW1. w I I I LIIII LII!I: r I I. fi MIIIIIIIIIUFILIII 1 I W r Patented Mar. 20, 1945 WELDINGMACHINE Hugo Purat, Detroit, Mich., assignor to Progressive WelderCompany, Detroit, Mich., a corporation of Michigan Application January2, 1943, Serial No.- 471,136

7 Claims.

The present invention relates to electric welding machines, and iparticularly directed to the provision of a machin embodyin improvementsover the structures disclosed and claimed in Hatch Patent No. 1,754,948,granted April 15, 1930, Martin Patent No; 2,126,490, granted August 9,1938, and in the copending application of the present applicant, SerialNo. 322,567, filed March 6, 1940, now Patent No. 2,287,945, granted June30, 1942. v

The present application is a continuation of applicants copending butnow abandoned application Serial No. 349,653, filed August 2, 1940.

The principal objects of the present invention are to provide a machinecomprising a plurality of pairs of electrodes, and further comprisingelectromagnetically actuated indexing mechanism to connect the pairs ofelectrodes to a source of power in predetermined sequence; to providesuch a system further characterized as embodying means operable aftereach electrode pair has been connected to the secondary winding of asupply transformer, to connect the primary winding of the transformer toa source of power; to provide such a, system wherein the operation ofthe indexing unit is controlled by timing means which are selectivelyadjustable to time the flow of welding current and to afford apredetermined timing interval between each such indexing movement; toprovide such a system wherein the timing means, in addition to operatingthe indexing unit, also actuates the means for connecting the primary ofthe welding transformer to the external circuit; to provide, for use inthe above as well as other machines, an improved electromagneticallyoperated indexing unit; and to provide an improved control system foreffecting the sequential operations of the machine.

With the above as well as other objects in view, a preferred butillustrative embodiment of the invention is shown in the accompanyingdrawings, throughout the several views of which corresponding referencecharacters are used to designate corresponding parts and in which:

Figure 1 is a View in front elevation. of a machine embodying theinvention;

Fig. 2 is a View in side elevation, corresponding generally to Fig, 1,but showing the movable electrodes in their lower or operativepositions;

Fi 3 is a View in vertical section, taken along the line 33 of Fig. 1;

Fig. 4 is a view in vertical section, taken-along the line 4-4 of Fig.1;

Fig. 5 is a fragmentary view, taken along the line 55 of Fig. 1;

Fig. 6 is a view in elevation, taken along th line 6-6 of Fig. 2;

Fig. 7 is a view in horizontal section, taken along the line 1-1 of Fig.6; and,

Fig. 8 is a diagrammatic view of a control system, which may be, andpreferably is, used in the practice of the invention.

It will be appreciated from a complete understanding of the presentinvention that the improvements thereof may be embodied in various formsand may be utilized for various specific purposes. By way ofillustration, but not of limita tion, the invention is herein disclosedin connection with a machine of the same general type as is disclosed insaid copending application.

Referring particularly to Figs. 1 and 2, the present machine comprisesgenerally a supporting frame arranged to provide a horizontalworksupporting table 20, and having uprights 22, which afford ways (notshown) to accommodate vertical reciprocating movements of a movableelectrode carriage 24. The movement of the carriage 24 between theelevated position shown in Fig. 1, and the lower or welding positionshown in Fig. 2, is controlled by suitable means, illustrated ascomprising a pair of ram 26, the cylinders whereof are stationarilysupported upon the main machine frame, and the piston rods 28 whereofare connected to the movable carriage 24. The table 2!! supports aplurality of stationary electrodes 30, which are insulated from theframe of the machine by an insulating support member 32, but which areelectrically connected to a bus bar 34. The bus bar 34, in turn, ispermanently electrically connected, as by the lead 35, to one terminalof the secondary winding of a transformer 38, which is mounted in thebase of the machine.

The movable carriage 24 carries a plurality of resiliently mountedmovable electrodes 36, one whereof is individual to each of theabove-mentioned stationary electrodes 30. It will be appreciated thatwhen the carriage 24 is elevated, the movable electrodes 36 arepositioned in spaced relation to the cooperating stationary electrodes30, and that when the carriage 24 is moved downwardly to weldingposition (Fig. 2), the work (indicated at 40 in Fig. 2) is clampedbetween the several pairs of stationary and movable electrodes 30 and3B. As is set forth in said copending application, the moving andstationary electrodes may be variously arranged at various elevationsrelative to each other and in various configurations and angularrelations to the supporting table 20, depending upon the character ofthe work to be welded. For purposes of illustration in the presentinstance, the moving electrodes are illustrated as being verticallydisposed, and a bein arranged in two series, one series being arrangedadjacent the front of the machine and a similar series being arrangedadjacent the rear of the machine.

In further accordance with the arrangement disclosed in; theabove-identified copending application, the movable electrodes 36 areresiliently supported, so as to enable them to yieldingly engage thework to be welded. Referring particularly to Fig. 3, each movableelectrode 36 is secured in a block 42, which block is attached to, butinsulated from, a rod 44,v by means of a sleeve 46. Each rod 44 isslidably. supported, for limited vertical movement, in a, pair ofthreaded sleeves 48 and 59, which sleeves are mounted in the flanges ofa channel-shapedbartZ. The respectively opposite ends of the bar 52areyfixed-ly mounted upon the frame 24 by means of hangers 54. Each-rod44, and consequently eachassociated electrode 36, is continuously urgeddownwardly relative tothe bar 52 bymeans of a compression spring 56, oneend whereof bears against the sleeve 43,-and the other'end whereof bearsagainst a washer, which seatsagainst ashoulder 69 formed on the rod.Each spring 56 is enclosed within a pair of telescoping shells GI and92. It will be observed that the sleeve 59, against which the washer 99bears; determines the limit of downward-movement imparted" to therod 44by the spring -56, whereas" the'sleeve 49 affords an adjustment of thespring 56, so as to vary-its tension and consequently vary the pressureexerted between the stationary e1ectro'de'39 and a cooperating movableelectrode-36.

' In furtheraccordance with the disclosure of the above-identifiedcopendin'g application, each electrode supporting block 42 ispermanently electrica-lly connected, by means of a flexible lead, suchas the lead "IU of Fig. 3, to a corresponding electrode-switch "I2, onewhereof is'individual to eachmovable electrode.- Each electrode switchI2 comprises a cylindrical body 14-, formed of conducting material, andpermanentlyconnected to the associated lead- ID by means of a connectingblock 16. Also, each switch body is permanently connected to,-butinsulated from, a bus bar I8,

by'means of studs 89" and insulating gaskets 82..

The two bus bars I8, one being provided for each series of electrodes36, in turn, are carried by a support 84, fixedly supported at its endsin the movable frame 24} Thebus'bars 'IS'are also permanentlyelectricallyconnected' to the other terminal of the transformersecondary, as by aplurality of flexible leads 86, which fiexible'leadsaccommodate the vertical movements of the carriage 24. j

Each switch comprises a stationary contact member 99 having an angledupper surface 9| for co-operation with the correspondingly angled lowersurface 93 of a co-operati'ng contact member 92. The contact member99 iswedged in a tapered bore formed in the bus bar 78 and thus isstationary. :The' contact member 92 i vertically slidable withinthe-bore formed in the switch body 14 and iS-' normally retained in theillustrated upper position in which the angled surfaces are separated,by means of a compression spring I96.

. The compression spring I 99 is seated in a counterformed upperendofthe core I2 comprises a coil I09, which is supported upon a corepiece I04. The coil I90 is enclosed by means of a shell I92 and a coverplate IUI which elements, it will be appreciated, are formed of magneticmaterial and thus constitute a part of the magnetic circuit of thesolenoid. The armature structure for the solenoid comprises thecylindrical member 98, which receives a threaded adjusting screw 99, thelower end of which adjusting screw bear against the headed member Themember II]? is loosely received in the bore of the core piece I94, anddownward force applied to the member IIl'I is transmitted to the collar94 through a washer I3 and a compressible cushion 9.6. -'I;he upper endof the member I91 isreceived in the-bore provided in the armature member98, and thus serves to guide said armature --member. It will beappreciated that by threading the stud 99 into or out of the member 98,the initial air gap between the conical lower end of themember 98-and'the'complementarily piece I04 can be varied.

It will further be appreciated that when the coil I99 is energized, thearmature member 98 is drawn downwardly, and'by means-of the stud 99,this movement is transmitted to'the member I01, which thereupon forcesthe contact 92 downwardly into wedging engagement with the contact 99.This wedging movement causes the surfaces 91 and 93 to wipe across eachother and in accordance with the disclosure of said Patent No.2,126,490, this action Wedges the contact 92 into lateral engagementwith" the bore of the switch body'14. An'efiicient electrical connectionis thus made, through the contacts 99' and-92, between the bus bar I8trode'36;

- It is desirable to enable the armature member 98 t move downwardly farenough to engage the core piece I94, thus closing the previouslymentioned air gap, and it Will be appreciated that the compressiblemember 96 is proportioned to accommodate such final movement of thearmature member 98. The sequential opening and closing of the electrodeswitches, the opening and closing of the primary circuit of the-supplytransformer, and the duration of each welding impulse, which resultsfrom the closure of the'primary circuit, are controlled by the indexingand control unit, which is designated as a whole in the various figuresas I20. Referring particularly to Figs. 4, 6 and 7, the indexing andcontrol unit' I29 comprises a commutator I 22 which is stationarilysupported by the frame I26 of the unit and is enclosed'by a split coverhaving a rear half I21 and a front half I28. The rear half I27 isrigidly secured to the frame I28, and the front half I28 is hinged tothe rear half, as most clearlyappears in Figs. 1 and2. The commutatorI22 comprises a series of circumferentially arranged conducting segmentsI39, which are insulated from each other by usual segments I32ofinsulating material, and which are supported upon a backing member I24.The backing member I24 has an integral adapter portion I25 which isthreaded into a c'ounterbore in the housing member I26.

The segments I30 are successively engaged, one at a time, by a movingbrush I23, which is supported to engage the lower face of the commuandthe associated movable electator. The brush I23 is carried by a usualbrush rigging I34, which is removably and adjustably secured to thelower end of the shaft I29 of the housing I26, and thus affords a thrustbearing element for the shaft assembly.

It will be noticed that the ratchet wheel I50 and drag plate I52 arefixed in place axially of the shaft I29 by means of the shoulder I56formed on the shaft and by means of a sleeve I42 which is fitted overthe shaft I29. The shaft. I29, ratchet wheel I50, drag plate I52, sleeveI42 and brush rigging I34 are maintained in assembled relation to eachother by a holding nut I4I, which is threaded onto the lower end of theshaft I 29. The nut I4I draws the rigging into solid engagement with thelower end of sleeve I42 and wedges the ratchet wheel I50 and drag plateI52 between the upper end of the sleeve I42 and the shoulder I56, asaforementioned. If desired, a locking set screw I35 may be threaded intothe opening provided therefor in the brush rigging so as to more firmlysecure the latter in adjusted position relative to the shaft I29. I

The sleeve I42 is rotatably received in the previously mentioned bearingboss I54 and thus gives radial bearing support to the entire shaftassembly. A second radial bearing surface I36 on the shaft I29 isreceived in a boss I40 provided in the removable cover for the housingI26,

The ratchet wheel I50 is directly actuated by a pawl I60 of usual form,which is carried at the end of a lever I62. More specifically, the pawlI60 is pivotally supported upon a pin I64, which pin is secured to thearm I62, and it will be understood that the pawl I60 is provided with aspring IBI to yieldingly bias it in a. counterclockwise direction, asviewed in Fig. 7. The lever is pivotally supported by the shaft I29, andi received between a shoulder I66 formed on the shaft and the ratchetwheel I50. j

The lever I62 is rocked to thereby advance the shaft I29 in step-by-stepmanner by means of an assembly, comprising the slide I14, a collar I 82and a push rod I84, which are operatively connected to an actuatingsolenoid U6. The slide I14, which is of generally U-shaped form, asviewed in Fig. 7, is guided in ways I16, I18 and I80 secured in thehousing I26, and is reciprocable between the lefthand limit position,shown in Figs. 6 and 7, and a normal position to the right thereof, Theslide I14 is provided with a transverse notch I12 in its upper surface,which receives a roller provided at the end of the lever I62 remote fromthe pawl I60.

The collar I82 is slidably mounted in a boss I86, which is threaded intothe body of the housing I26, and is provided with a biasing spring I88,which is seated between a shoulder I90 formed on the push rod and theway I16. which spring serves to continuously urge the collar I82 to theright, as viewed in Fig. '7. The collar I82 is further provided with acounterbore which receives the enlarged head I92 of the rod I84, andwhich also receives a biasing spring I94, which acts to continuouslyurge the rod I84 to the right relative to the collar I82.

The rod I84 passes through the collar I82 and also passes looselythrough a bore formed in the position.

slide I14, and at its lefthand end is provided with a head I96, which isreceived in a counterbore I98 formed in the slide I14. The head I96affords a means for moving the slide I 14 to the right, and also affordsa means for operatin the tappet 200 associated with a control switch202. The switch 202 may be and preferably is of usual form, having apair of contacts arranged to occupy the open position at all timesexcept when the operating arm 204 thereof occupies the'lefthand limitposition, shown in Fig. 6. As clearly appears from Figs. 6 and 7, whenthe push rod I84 travels to the left, the head I96 thereof bears againstthe tappet 200, which is adjustable in length, and forces the operatingarm 204 to r0- tate in a clockwise direction. The arm 204 is preferablyprovided with means to move the same in a counterclockwise direction assoon as the biasing force of the tappet 200 is relieved.

The rod I84 is provided at its righthand end with a tappet 2 I 0, whichis adapted to be engaged by a roller 2| 2 provided on an operating arm 2of hell crank form, associated with the solenoid 2I6. The bell crank 2I4is pivotally supported upon a pin 2I1, and is connected to the armature2I8 of the solenoid by means of a usual link 220. With this relation, itwill be understood that an upward movement of the armature 2I8,resulting from an energization of the solenoid 2I6, swings the bellcrank 2I4 in a clockwise direction and forces the rod I84 to the left,bringing it to the position shown in Figs. 6 and '7.

The force applied to the rod I84 is transmitted to the collar I82through the spring I94, which is heavier than spring I88. As aconsequence, the just-mentioned force causes the collar I82 to movetoward the lefthand position shown in the various figures, compressingthe spring I88 and forcing the slide I 14 to move toward the lefthandThe just-mentioned movement of the slide I14 is operative, by virtue ofthe roller I68, to rock the lever I62 in a counterclockwise direction.The latter movement enables the pawl I to impart a predetermined angularadvance to the ratchet wheel I50, which action correspondingly advancesthe brush I23, moving the same from a position in engagement with onecommutator segment I30 to a position into engagement with the nextsuccessive commutator segment. As the slide I14 reaches the lefthandlimit position, the angled lower surface 22I thereof rides into thespace between successive teeth of the ratchet wheel I50, locking saidwheel against movement in either direction until such time as the slideI14 is moved to the right out of the locking position. When the slideI14 reaches its lefthand limit position, further movement thereof isprevented, correspondingly preventing further leftward movement of thecollar I82. Continued leftward movement of the rod I84, therefore,compresses the spring I94. The parts are preferably so proportioned thatthe control switch 202 is not closed by the tappet 200 until after theslide I14 has reached its lefthand limit position and completed thenotching advance of the ratchet wheel. The amount of such furthermovement of the rod I 84, which is needed to close the switch 202, can,of course, be varied by adjusting the length of the tappet 200, and inthis connection, it is noted that the tappet 2I0 is also of adjustablelength, the preferred adjustment being one wherein the armature 2I8 ofthe solenoid 2I6 is enabled to have its full movement. The tappet 2 I 0is adjusted, as will be appreciated, by rotating the same on the stud222, which stud is-threaded into the counterbored end of theenlarg'edf'head I92 of the rod I84.

When the solenoid 2I6'is .de-energized, the spring I88 is enabled toreturn the collar I82 to its righthand limit position, carrying with itthe rod' I84. Thelatter movement enables the head I'SG tobear againstthe lefthand end of the slide I14 and move the latter to its righthandlimit, and'also swings the bell crank 2M, associated with thesolenoid,to its inactive position. During" the. return movement of theslide I'M, the pawl I80 rides over the teeth'of the ratchet wheel I56without causing any movement thereof, since the ratchet wheel is subjectto the frictional drag action of the previously mentioned drag plateI52, and also sincethe commutator I22 is subject to "the drag action ofthe brush I23. "The initial rightward movement of the'rod I84 alsoenablesthe usual spring means (not shown) associated with the arm 294 ofthe control switch 2H2 to open the contacts associated with the latter.

' 'In order to enable the indexing and control theclosure ofthe; switch202 does notoccur until after the angular advances of .thecommutatorI22v and of the control, drum 230*have' been. completed. Depending uponthe numberand disposition of the tappets, such as 240, each such advanceof the drum 230 may be caused to effect a closure of on or more, ornone, of the timing switches 25%, 25B and 258. .As is described withreference to Fig. 8, each such notching advance is preferably arrangedto close one of the-control switches 254, 256 and 258 and leave theother unit I28 to variably control the duration of each Welding impulse,this unit is provided, at the upper end 'of the shaft I29, with acontrol drum 230 of the type disclosed in the aforesaid copendingapplication. The control drum 230 is secured to the reduced portion 232of the-shaft I29, for rotation thereby, and is provided with threeseries of circumferentially distributed openings 234, 236 and 238. Theopenings of each series "are adapted to receive removable tappets, suchas 249, which tappets are arranged to cooperate with rollers 242, 244and 246, provided at the ends of push rods 2G8, 250 and 252, associated,respectively, with timing switches 254, 256 and 258. These controlswitches are provided with normally open contacts (not shown in Fig. 3,but shown diagrammatically in Fig. 8), which contacts are adapted to beclosed so' long as the corresponding push rod is depressed by a tappet240.

The indexing and control unit may be located either upon or remotelyfrom the machine, but is herein shown as being mounted upon, butinsulated from, th movable frame 24. With this relation, the leads, suchas I3I, from the commutator to the various electrode switches, which mayindividually be led from the unit I20 through one or more usual multipleplug and jack type junction boxes I2I, are not subject to flexure duringoperation of the machine. The leads from the timing switches 254, 256and 258, and from th control switch 202, are not shown except in Fig. 8,but it will be appreciated that these leads may be arranged toaccommodate the movement of. the frame 212. It is noted that the brushI23 is inv electrical connection with the housing I26 through the shaftI29, brush rigging IM and related parts, so that the connection for saidbrush, also. shown only in Fig. 8, may be made directly to said housingI26.

From the foregoing, it will be appreciated that each energization. ofthe solenoid 2I6 causes the indexing unit to advance through an angleequal to the angular spacing between adjacent teeth of the ratchet wheelI59, thereby causing a corresponding angular advance of the brush I23relative to the commutator and of the control drum 230 relative to thetiming switches. Such energization also, results in a closure of thecontrol switch 202, and maintains this switch closed as long as thesolenoid 2I6 is energized. Moreover,

control switches open. Accordingly, the preferred arrangement is onewherein the tappets, such as 240, are distributed between the seriesofopenings 234,235 and 238 in staggered relation, only one tappet-beingpresented to an associated switch push rod in each position of the drum.It will further be understood that while only three series of openingsand consequently only three switches are illustrated, larger or smallernum bers may be employed, if desired.

It will be appreciated that in the broader aspects of the inventiorranyof a variety of numerical ratios may be employed between the number ofteeth or positions of the ratchet wheel -I 50, and the number ofsegments on the commutator. It will also be appreciated that eachindividual segment on the commutatorcan be arranged to control one or agroup of the previously described electrode switches 12. In thepreferred and illustrated arrangement, however, each segment on thecommutator is arranged to control one such electrode switch and thecommutator is, there'- fore, provided with a segment individual to eachsuch switch. In addition, in the present instance, the commutator is'provided with an additional segment which effects the hereinafterresetting of the system. With the present arrangement, therefore, thenumber of commutator segments equals the number of teeth on the ratchetwheel I and each notching movement of the unit 'moves the brush I23 outof engagement with one segment and into engagement with the nextsuccessive segment. The number of openings in each of the series ofopenings provided in the control drum 230 correspondingly equals thenumber of teeth on the ratchet wheel At each notching position of thenotching unit, accordingly,v one pairof electrodes is supplied withwelding current for an interval determined by the mechanism controlledby the timing switches 254, 255 and 258, and during the course of a fullrevolution of the notching unit, all of the pairs of welding electrodesare given one such impulse of welding current.

It will be recognized that, in the broader aspects of the invention, anyof a variety of timing control and welding control systems may beemployed in conjunction: with the above described welding machine. Apreferred such con.- trol system is, however, illustrated in Fig. 8.

Referring particularly to Fig. 8, certain of the previously describedmechanical elements of the present system are shown diagrammatically andin addition, certain control relays and devices not previously describedare also shown. These additional elements maybest be described inconnection with a description of operation of the system as a whole, butit is here noted that they comprise generally a series of threeelectronic valves VI, V2 and V3, and related electromagneticallyoperated relays. Thev valves VI. V2 and V3 are of the three-elementtype, having a plate, a filament, and a control grid, charac- .terizedin that they remain conducting so long as a predetermined potential isapplied between the plate and the filament and so long as the potentialof the control grid is maintained at a predetermined value relative tothe potential of the filament. The valves remain non-conductive so long,however, as a so-called blocking potential is applied to the gridsthereof. The valve VI functions primarily in the present system toadvance the notching unit and complete a circuit through the secondarywinding of the welding transformer for the successive pairs ofelectrodes; the valve V2 functions primarily to control initial closureof the primary circuit of the welding transformer and to delay suchclosure until after the secondary circuit has been completed; and thevalve V3 functions primarily to terminate the welding period byinterrupting the primary circuit of the welding transformer and alsoserves to de-energize the solenoid 216 of the notching unit, therebyconditioning the same for the next succeeding notching movement.

The control system of Fig. 8 is illustrated as being supplied withalternating current from illustrative line conductors LI and L2, and thesystem may be conditioned for operation by closing the line switch 215.It will be understood that such closure may be arranged to supplyheating current to the filaments of the individual valves VI, V2 and V3,through conventional circuits which have been omitted in order tosimplify the drawings. In the present instance, closure of the lineswitch 216 also initially energizes a control transformer T4 associatedwith the grid of the valve V2, enabling such transformer to immediatelyapply a blocking potential to the grid of the valve V2 and render thelatter non-conductive. Closure of the switch 216 also energizes controltransformer T5, enabling the latter to apply a blocking potential to thegrid of the valve V3 and render this valve nonconductive.

Assuming it is desired to effect a welding operation, and that theworkpieces 40 have been positioned upon the stationary electrodes 30,the starting switch, herein illustrated as a manually operable pushbutton 210, may be closed, which action completes a circuit from theline conductor LI through the operating winding 212 associated with avalve 274 to the other line conductor L2. Upon being energized, thewinding 212 actuates the valve 214, which, it will be understood,actuates the previously described fluid rams 26, to lower the movableframe member 24 and bring the movable electrodes 35 down into clampingengagement with the workpieces 40, the degree of such clamping actionbeing determined, as will be understood, by adjustment of the electrodesupports described with reference to Fig. 3. The valve 214 is preferablyof the type which remains in the position to which it is moved uponenergization of the winding 212 until such time as the reset winding 280is energized. The starting button 210 is, therefore, required to beclosed only normally and the electrodes remain in clamping engagementwith the work until such time as the reset winding 280 is energized.

As soon as a desired clamping pressure between the movable and thestationary electrodes is attained, a usual pressure switch 282, actuatedby the frame 24, assumes the closed position, which action completes acircuit to energize the primary windings of the control transformers TIand T2. The latter action is without immediate effect, since asmentioned above, the valve V2 is blocked by the potential impressed onthe grid thereof by transformer T4. The energization of transformer Tlresults in the energization of the winding of control relay RI. Thewinding of relay R1 is connected in the closed plate circuit of valveVI, which, under present conditions, is in a conducting condition.

Upon being energized, relay RI closes its normally open contacts Rla.The closure of contacts Ric completes a circuit through the coil of thepreviously mentioned solenoid 2l6, associated with the indexing andcontrol unit I20. In accordance with the previous description, theenergization of solenoid 2H5 causes the brush I23 to advance from aposition in engagement with the reset segment, designated I301, intoengagement with the next succeeding segment I30. Such notching advancealso moves the drum 230 to a position in which one of the timingswitches 254, 256 and 258 is closed. After completion of the brushadvance, and after the par ticular timing switch is closed, the push rodI84 is enabled to close the control switch 202. The latter actiondirectly completes the circuit for the winding of a control relay R2. Assoon as the latter circuit is completed, relay R2 closes its contactsR2a, Which action energizes the brush I23, thereby completing a circuitthrough the brush 123, the then-engaged segment, and thence through thecoil I00 of the electrode switch 12, corresponding to the engagedsegment. Upon being energized, such coil I00 forces its associatedcontact 92 downwardly, completing a circuit between the associated busbar 18 and housing 74. In accordance with the previous description, thebus bar 18 is continuously connected to one terminal of the secondarywinding 280 of the welding transformer 38; the other terminal thereof isconnected to the stationary electrodes 0 3D. The housing of theenergized electrode switch is, in turn, directly connected to thecorrespond ing movable electrode 35. The just-mentioned initial notchingmovement of the control unit I20 therefore serves to complete a weldingcircuit, through the secondary of the welding transformer, for acorresponding pair of electrodes 3630.

The previously described closure of the relay contact Rla also completeda circuit for the primary winding of control transformer T6, therebyenergizing the secondary winding thereof and enabling the latter tooppose the potential impressed on the grid of valve V2 by transformerT4. At this time, accordingly, the energy stored within the condenserCl, associated with valve V2, discharges therefrom, and after apredetermined period determined by the characteristics of the gridcircuit, the grid of valve. V2 attains a potential at which it rendersV2 conducting. At this time, control relay R3 is energized through valveV2, by means of energy supplied from transformer T2. It is noted thatthe time delay provided by the timing condenser Cl is suificient toinsure the closure of the transformer secondary circuit prior to theclosure of relay R3.

Upon being energized, control relay R3 closes its contacts R3a and R32).The former contacts complete a circuit for the coil of the weldingswitch W, which circuit also includes the normally closed contacts R4aof control relay R4. Upon completion of the just-mentioned circuit, thewelding switch W closes its contacts Wa and connects the primary winding292 of the welding transformer 38 directly across the supply conductorsL3 and L4, resulting in a now of welding current between the previouslyenergized pair of welding electrodes 36-30.

The closure of contacts R31) completes obvious circuits for the primarywindings of control transformers T7 and T8. A The secondary windings 294and 296 of transformers T and Ts'areconnected in series with the grid38!] of valve V3. This grid circuit also includes, in parallel, thepreviously mentionedtiming switches 254, 256 and 258, one of whichtiming switches is now closed in accordance with the previousdescription. The several timing switches control, respectively, thetiming condensers C2, C3 and C4. Upon energization of transformer T8,accordingly, which opposes transformer T5, the potential previouslyapplied to grid 3% is dissipated at a rate determined by thecharacteristics of the timing circuit associated'with the closed one'ofthe timing switches 254, 258 and 258. At the end of an intervaldetermined by the characteristics of the active timing circuit, thepotential on grid 300 falls to a value at whichvalve .V3 becomesconductive. At this time, thepreviously energized transformer Tisenabled toenergize control relay R4, which thereuponopens its contactsRda and RED, and closes itscontacts R40.

The opening of contacts R'da interrupts the drcuit for the. weldingswitch W, terminating the flow of Welding current. i

The .opening of contacts R lb de-energizes transformer T1, therebyinterrupting the supply of energizing currentto the .coil of relay RI,and, after .a brief period determined by the condenser C.5, re1ay RIresumesthe. de-energized position,- opening thecontacts R] a.

The closure .of contacts R60 energizes transformeriT3, which thereuponapplies a blocking potential to the grid of vvalve VI, fora purposedescribed below. The opening of contacts litla de-energizes the solenoid216 of the notching unit, and also de-energizes the controltransformerTfl-which thereupon restores the valve V2 to itsoriginalnon-conducting condition, and .interrupts the energizing circuitfor relay R3. The de-energization of relay R3,. which occurs after abrief period, determined by the characteristics of the associatedcondenser C6, causes the contacts RM and R3b-to open. The opening of.contacts Rita. is without immediate efiect in view act the previousopening of contacts .R lrz'. The .openingof contacts R3bde-energizestransformers T'I' and-T8 The de energizationcof these transformersinterrupts the energizing circuit for the winding of relay R4 and alsorestores the valve V3 .to. its original non-conductive condition.Afterha brief interval, determined by the characteristics of theassociated condenser Cl, relay R4 resumes the de-energizedposition,again closing contacts Rdaand R41) and opening contacts RAc. The closureof contactsR lais Without effeet at this time, since; contacts R3a areopen. The closure of contacts R41) again energizes transformer Tl inpreparationfor-the next welding interval. The-opening of.contacts'Rcinterrupts the energizingcircuit for transformer T3, and,as, is discussed below, at the'expiration of a period which isdetermined by the characteristics of the timing circuit, includingcondenser C8, valve Vi again becomes conducting.

The de-energization of solenoid 216, which resulted from the opening ofrelay RI, enables the push rod i'il lto moveto the right,.as previouslydescribed, during the. initial stages of which movement. control switch292 :resumes the open.

positionde-energizing control relayRZ; Therlatr,

ennui? ter' action interrupts the circuit through 'th'e brush 1 23 :ofthe notchingmnit, thereby de energizing the: previously energizedelectrodeswitch 12 and interrupting the secondar-y transformer circuitthrough the initially actuatedpai-r' 'of welding electrodes 1-8-30. Thecontinued-rightward movement of-the push .rod lBfl also restores thenotching pawl mechanism to theirighthand limit position thereof, therebyconditioning the same for .a succeeding notching operations From theioregoingit will be observed that the closure of the startingbutton 2T0initially brings all of the movable electrodes down'into clamp ingengagement with the Work and thereafter causes the notching unit toadvance to the firs't operating position. Upon reaching the first-opcrating position, the notching unit first completes the secondarytransformer circuit for the corre a circuit forthe solenoidofthewelectrode switch;-

sponding first pair'of electrodes and thereafter causes completion ofthe primary circuit of the welding transformer, initiating the firstweld-ing interval. The timing system interrupts the primary circuit ofthe transformer at the conclusion of the just-mentioned first interval:andthere after causes the notching unit to interrupt the originallycompleted secondary circuit and as sume a condition in readiness forthe-next notching operation.

So long asa .blocking .potential isnma'intained on the grid of valve.Tv'l by means of the timing circuit, including "condenseriCii, thelsystem -re' mains .in the same condition .as ohtainedammo the initialclosure .of thehpressur'e -switch 282 l That is to say, relays R1,:R2,R3 and R4 occupy the lie-energized positions and blocking potentials areapplied to the grids "of. valves VZ and -V3 through transformerszTA and'T5.'" The timing interval provided by. the timing circuit,- includingcondenser C8, determines the time interval between successive weldingintervals; This-time interval .is' preferably. set; to slightly exceedthe time required for the notching unit to re'set itself after theinitial dee'energization ofth'eiis'o-lenoid 21.6. r I

At the expiration of thetime interval :affiorded by the timing circuit,"including .icondenserca; valve VI again-becomesconducting :andy'sincetransformer T! is'still energized-through'the pressureswitch 282,transformer TI is enabledto re-energize .control relay .Rl'. It-isbelieved to be evident that the re-energization .oftcontrol relay: RIagain energizes the solenoid-:2 1 6:0? the notching unit, causingthebrush 1.2.3 to advanceto' thernext succeeding segment, and alsd energizes transformer Tfipso as to conditionvrelay- R3 for operation. Also,theoperation-of' the notching unit advances the timing drum' 23ll onenotch, in which second position it again:

closes one ofthe timing switches 25d;:256=and 258. The operation ofthenotching 'solenoid'also closes the control relay. R2; therebycompletingcorresponding to the nowengaged: commutator segment. Thetiming period rovided by valve V2 again allows timeto complete thejust-mentioned: secondarycir'cu-it and. thereupon re-completes theprimary circuit. The remaining operations also correspond to thosedescribed above, the length of theuwelding interval in-this-icasebeing'determinedby'that one of the timing switches- 254, 25$:and2-58; whichoccupies the closed-posh tiOnr".

long, accordingly, las the. pressure-switch 262 :remains. closed, thetrespective pairs of elec' trodes. .are successively csuppli-ed--withweldingcurrent for periods determined by the timing drum, eachsecondary circuit being completed prior to completion of the primarycircuit and being opened only after interruption of the primary circuit.Only two of the electrode switches are shown diagrammatically in Fig. 8,but it will be appreciated that the remaining indicated circuitsconnected to the respective commutator segments lead to the otherelectrode switches in the same manner as is indicated for theillustrated two electrode switches.

It will be appreciated that it is usually desirable in welding systemsto maintain the elec trodes in clamping engagement with the work for aninterval following the termination of the flow of welding current. Inthe present, system, all of the electrodes remain in clamping engagementwith the work until after the entire cycle is completed, so that specialprovision for the just-mentioned hold time need be made only inconnection with the last pair of electrodes. In the present instance,this hold time is afforded by the timing condenser C5, associated withthe relay RI, the discharge current whereof maintains the relay RIenergized for a short interval following the de-energization of thewelding switch W. At the conclusion of the welding interval for the lastpair of welding electrodes, and after the just-mentioned hold timeprovided by condenser C5, relay RI again resumes the openposition, andas before, de-energizes the notching solenoid 2I6, carrying the notchingunit for movement to the original position in which the brush I23engages the reset segment I301. Also at the expiration of the timinginterval provided by condenser C8, valve VI again becomes conductive andre-energizes relay RI. The re-energization of relay RI again energizesthe notching solenoid 2 I 6, which thereupon advances the notching unitto the justmentioned reset position and closes the control switch 202,energizing relay R2. As a consequence of these actions, a circuit iscompleted through the brush I23, and the reset segment I301 for thereset coil 280 of the valve 214, which thereupon applies power to therams 26 in such relation as to cause them to elevate the movableelectrode frame 24 to the position shown in Fig. 1. The initial liftingmovement of the movable electrode frame 24 relieves the pressure on thepressure switch 282, allowing the same to open, interrupting thecircuits for transformers Ti and T2. The latter action is withoutefiect, since valve V2 is already in a non-conductive condition, but thede-energization of transformer TI again tie-energizes relay RI. Thisaction de-energizes the notching solenoid 2I6, allowing the ratchetmechanism to resume its normal position and also opens switch 202,de-energizing relay R2. The latter action interrupts the circuit for thevalve winding 280, which action is, however, without eifect since thevalve is now in the position corresponding to the elevated position ofthe movable electrode frame.

The reclosure of relay RI, which, as above stated, restored the notchingunit to its original position, also re-energized transformer T6, tendingto re-energize relay R3 and recomplete the welding circuit. As describedabove, however, the energization of relay R3 is delayed, following theclosure of relay RI, for an interval determined by the timing condenserCI. This timing interval is adjusted, not only to allow sufficient timeto close the welding transformer secondary circuit before the primarywelding circuit is closed, but also to allow, under the conditions,

stated, for the opening of pressure switch 282 before relay R3 recloses.As soon as the pressure switch 282 is open, and de-energizes transformerT2, the energization of relay R3 is, of course, prevented.

At the conclusion of the above described complete cycle, the elements ofthe control system occupy the same positions as they occupiedimmediately prior to the initial closure of the starting button 270, andfurther complete cycles may, of course, be initiated by reclosing thebutton 210.

The switch structures principally illustrated in Fig. 3 are claimed inapplicants Patent No. 2,353,847, issued July 18, 1944, on applicationSerial No. 462,452, filed October 15, 1942. The indexing mechanism shownin detail in Figs. 4 through '7 is claimed in applicants co-pendingapplication Serial No. 554,596, filed September 18, 1944, as acontinuation of application Serial No. 462,451, filed October 15, 1942,said applications Serial Numbers 462,451 and 462,452 being divisions ofapplicants parent application Serial No. 349,653, filed August 2, 1940.The present application is a continuation of said parent applicationSerial No. 349,653.

Although only a single complete embodiment of the invention has beendescribed in detail, it will be appreciated that various modificationsin the form, number and arrangement of parts may be made within thespirit and scope thereof.

What is claimed is:

1. In an electrical control system for controlling the flow of currentfrom a source of load current through a plurality of electric energyconsuming devices, the combination of means including circuitconnections and a plurality of electroresponsive switches for connectingsaid devices to said source, said switches being actuable betweencircuit interrupting and circuit closing conditions, one said switch andthe corresponding circuit connections being individual to each saiddevice and each said switch having energizable means eifective uponbeing energized to actuate the corresponding switch from one saidcondition to the other, circuit commutating means, and means renderedeffective by said circuit commutating means for controlling the supplyof energizing current to the said energizable means to thereby cause thesame to successively interrupt and close the circuit connections to thecorresponding devices.

2. In an electrical control system for controlling the flow of currentfrom a source of load current through a plurality of electric energyconsuming devices, the combination of means including circuitconnections and a plurality of electroresponsive switches for connectinsaid devices to said source, said switches being actuable betweencircuit interrupting and circuit closing conditions, one said switch andthe corresponding circuit connections being individual to each saiddevice and each said switch having energizable means eifective uponbeing energized to actuate the corresponding switch from one saidcondition to the other, circuit commutating means, means renderedefiective by said circuit commutating means for controlling the supplyof energizing current to the said energizable means to thereby cause thesame to,successively close the circuit connections to the correspondingdevices, and timing means for controlling the supply of energizingcurrent to said energizable means to thereby determine the period duringwhich each switch-is efiective toi'close thecircuit connections tothcorresponding devi'ces and forcausingnaoh such switch to interrupt thecorresponding circuit connections, s. l l l 3. In an eleotricallcontrolsystemufor control ling the flow of current from a source ofLloadcurrentthrough a plurality of electricene-rgy consuming devices, thecombination of means including circuitrconnections and a plurality ef56160- troresponsive switchesfor connecting saiddevices to .said source,said switches being lactuable be-; tween circuit interrupting andcircuits. closing conditions, one said switch and the correspondingcircuit connections beingcindividual to leach zsaid device and each saidswitch having energ'izable means effective upon being energized toactuate ascent-7 efiective' to close the circuitcdnnectiiahs to "thecorresponding device "and'ifo'r --causing each such swito'hto interruptthe corr-esponding circuit connections5and means rendering said timingmeans effective to control said circuit commutating meansym N, ,ll 1w KP;

4. The combination defined "by claim -=l including switch-means commonto said-' devicesand operable in timed relation to said elec'troresponsive switches.= a

5. The combination defined by claim -1 including control means to enablecertain of said switches to cause deliveryotcurrentto the cor- HUGOPURnn

